Non-lactating Females Research Articles

Reduced Progesterone Metabolites Are Not Critical for Plus-Maze Performance of Lactating Female Rats

Lactation has been associated with anxiolysis in several tests of anxiety. These observations, considered together with observations that progesterone and its 5α-reduced metabolites are anxiolytic in cycling, nonlactating females, raised the question of whether the changes in anxiety-related behaviors that accompany lactation are driven by reduced progesterone metabolites. Lactating female rats were tested on the plus-maze on postpartum days 2 or 7, and demonstrated enhanced open-arm performance relative to cycling, nonlactating females. Hormonal analysis indicated that while serum levels of both progesterone and its 3α,5α-reduced metabolite were increased in lactating females, the turnover of progesterone to the metabolite was markedly reduced during lactation. Furthermore, treatment with a 5α-reductase inhibitor for 3 days prior to testing potentiated the open-arm performance in lactating females, implying that enhanced open-arm performance was not mediated by the reduction of progesterone or other steroids. Additionally, analysis of GABA A receptor function indicated that parturition and lactation did not alter the sensitivity of the receptor to GABA or to modulation by reduced steroids. The mechanisms driving enhanced plus-maze behavior in lactating females appear to differ from mechanisms identified in nonlactating females.

Factors affecting velvet antler weights in free-ranging reindeer in Alaska

<p>Free-ranging reindeer on the Seward Peninsula in western Alaska are rounded up from late May to early July and antlers are removed. We used data collected from 1987 to 1997 to determine how velvet antler weights of males and females varied with age, year, reproductive status, Julian date, and body weight. Male antler weights increased with age up to age five years, and were lower in castrates than in bulls. There was a significant positive relationship between body weight and antler weight in both sexes. Female antler weights increased with age until at least age nine. Lactating females had lower antler weights than non-lactating females, but this effect is better explained by differences in body weight. Antler weight of individual reindeer at age two years was better predicted by their antler weights as yearlings than their body weight as yearlings.</p>

The influence of fatness on the likelihood of early-winter pregnancy in muskoxen ( [formula omitted

Among wild ruminants, muskoxen have an exceptional ability to fatten, but their pregnancy rates are variable and often low. To test whether the likelihood of pregnancy in muskoxen is associated with exceptionally good body condition, we used logistic regression analysis with data from 32 pregnant and 18 nonpregnant muskoxen ≥ 1.5 yr of age shot in November (1989 to 1992) on Victoria Island in Arctic Canada. We assayed their serum for insulin-like growth factor-1 (IGF-1). All fatness and mass measures were positively related to the likelihood of pregnancy (P < 0.001), with the strongest associations for estimated total fat mass (80 % of outcomes predicted correctly) and kidney fat mass (77 %), and weaker models for body mass. Pregnancy was less likely to occur in lactating females than in nonlactating ones (P = 0.03). Although IGF-1 concentrations were higher (P = 0.001) in nonlactating females than in lactating ones (28.7 ± 1.7 vs. 22.5 ng/ml), no association with pregnancy was detected (P = 0.57). Fatness associated with a 50 % probability of pregnancy in muskoxen (22 % of ingesta-free body mass or 32 kg fat in females > 3.5 yr old) is much higher than in caribou and somewhat higher than in cattle, and this may partly account for the low calving rates often observed in this species.

Percutaneous penetration of Aldara™ cream, 5% during the topical treatment of genital and perianal warts

Objective: The objective of this single-center, open-label trial was to evaluate the percutaneous penetration of Aldara™ (imiquimod) cream, 5% when applied topically to patients with anogenital warts using a more frequent/aggressive dosing regimen. Methods: Ten otherwise healthy males and six otherwise healthy, nonpregnant, nonlactating females with histology results suggestive of, or diagnostic of, human papilloma virus/condyloma acuminata were enrolled. Females were required to be practicing an acceptable form of contraception control. Patients applied cream daily (8 ± 2 hours) until complete wart clearance, or for a maximum of 16 weeks. Following the initial dose, at approximately week 4, and at the end-of-treatment, patients were confined for 42 hours in order to obtain a series of blood and urine samples. These samples were analyzed for levels of imiquimod and two metabolites, S-26704 and S-27700. Biological marker levels were not included as a part of this trial. Results: No quantifiable (≥5 ng/mL) levels of imiquimod or the two metabolites were observed in any of the serum samples collected. Five patients had quantifiable (≥10 ng/mL) imiquimod, S-26704, or both in urine. No quantifiable levels of S-27700 were observed. Complete clearance of warts occurred in 40% of male patients and 83% of female patients. Erythema was the most frequently observed local skin reaction and was moderate in intensity, although 6 of 16 patients reported a severe erythema reaction at some point in the study. Application site reactions (itching, burning and pain) were the most frequently reported adverse events. Conclusion: The lack of quantifiable levels of imiquimod or metabolites in serum, together with sporadically occurring quantifiable but low levels in urine, indicate that systemic exposure, after daily application of Aldara cream to genital/perianal skin, may occur but is minimal; however, pharmacological (immune marker) effects were not evaluated because cytokine measurements were not obtained. A future trial assessing cytokine levels after topical Aldara therapy with minimal systemic levels of imiquimod would help assess systemic drug and pharmacological effects and utility of this product in pregnant women.

Topographical Distribution of the Blubber of Harbor Porpoises (Phocoena phocoena)

Thickness of blubber was measured at 48 sites on the bodies of 68 male and 46 female harbor porpoises ( Phocoena phocoena ) from the Bay of Fundy, Canada, and Gulf of Maine and mid-Atlantic coast of the United States. Blubber was thinner over the head than in the thoracic-abdominal region, where thickness varied little around the girth of the animal. Thickness of blubber anterior to the anus ranged from 15 to 25 mm. Posterior to the anus, blubber formed thick dorsal and ventral ridges but was extremely thin laterally. In the thoracic-abdominal region, blubber of calves ( X = 22.9 mm ± 3.6 SD; n = 11) was significantly thicker than that of all other animals, but lactating females had the thinnest blubber (14.5 ± 3.1 mm; n = 7). Immature porpoises of both sexes, mature males, and non-lactating mature females had thicknesses of blubber intermediate between those of calves and lactating females. Thickness of blubber anterior to the anus was correlated negatively with body size, an unusual relationship for a marine mammal. Blubber posterior to the anus was similar among reproductive classes. Blubber of the harbor porpoise appears to be divided into two functional components. The thoracic-abdominal blubber functions primarily as an energy store and insulation, and posterior blubber acts to maintain hydrodynamic shape on the peduncle. Calves and adult porpoises may have different thermoregulatory and energetic strategies, resulting in different adaptations of blubber structure.

Torpor in lactating Siberian hamsters subjected to glucoprivation.

Daily torpor has never been reported for any rodent species during lactation. To test whether torpor and lactation are incompatible processes, we administered 2-deoxy-D-glucose (2-DG), a glucose analog that interferes with cellular glycolysis, to Siberian hamsters during the 2nd wk postpartum. 2-DG (2,500 mg/kg of body mass) induced torpor in lactating as well as nonlactating females. Although depth of torpor did not differ between groups, duration of torpor tended to be shorter in lactating animals. Evidence of new milk bands suggests that pups were able to obtain milk from torpid dams. By contrast, dams subjected either to a combination of brief food deprivation and subsequent food restriction or just food restriction failed to display torpor, but instead cannibalized one or more pups. We conclude that torpor is possible during lactation; whether lactating dams in nature become torpid in response to energy shortages or cannibalize or abandon one or more of their offspring remains unknown.

Age-related changes in ovarian morphology from birth to menopause in the Japanese monkey,Macaca fuscata fuscata

Age-related changes in ovarian morphology were studied in female Japanese monkeys,Macaca fuscata fuscata. A total of 47 nonlactating females of various ages ranging from new-born to >28 yr old were used. Ovarian size increased during the first decade of life, reached a plateau at around 10 yr. This was followed by a gradual decline throughout the remaining life span. The ovarian cortex of new-born animals consisted of numerous clusters of mitotic primordial germ cells. Such mitotic germ cells were observed even in the ovary of 28-day-old animal, but were not found in any animal after 1.5 yr of age. Numbers of primordial follicles decreased exponentially with the advance of age, and only a few primordial follicles were observed after about 16 yr of age. The numbers of primary and tertiary follicles increased from ages 4 to 16 yr, with a peak at 8 to 10 yr, and then decreased gradually. Developing tertiary follicles were observed as early as 1.5 yr of age. About 40% of tertiary follicles were atretic follicles throughout life, and their size was similar to that of developing tertiary follicles. Corpora lutea or corpora albicantia were found in ovaries more than 4 yr old. Remnants of corpora lutea and corpora albicantia, together with thick-walled blood vessels and fibrosis, became apparent in ovaries after 16 yr, and were observed characteristically in ovaries over 26 yr of age. There was no significant difference in the number or in the size of tertiary follicles between the breeding and nonbreeding seasons.

Lasion of hypothalamic paraventricular nucleus and maternal aggressive behavior in female rats

Lactating female rats on the 3rd to 12th day postpartum are more aggressive towards an intruder male than are nonlactating females. In this study, maternal aggressive behavior was recorded by introducing a strange male in the territory of the female and her offspring, on the fifth, seventh, and ninth day postpartum. Electrolytic lesions of the paraventricular nucleus of the hypothalamus (PVN) were performed on the fifth day postpartum. The results showed that the PVN lesion reduced the frequency and duration of attacks on the intruder. In addition, the lesion caused reduced weight gain in the pups compared to pups of the sham lesion group. The results suggest that PVN participates in the modulation of maternal aggression in rats. A possible role of oxytocin in that behavior is discussed.

In quest for a possible association between heightened social aggression and excessive alcohol drinking in the rat

Many clinical studies show that a sizeable proportion of male alcoholics are also inclined to act violently and aggressively. Given this association in humans, we asked whether a relationship exists between ethanol intake and aggressive behaviour in laboratory rats. In a first test of the hypothesis, we measured ethanol intake in male rats made aggressive by periodic contacts with sexually active females. Although the males became significantly more aggressive, there was no concomitant enhancement of alcohol consumption. In other experiment, observations of ethanol drinking in lactating rats exhibiting maternal aggression revealed no alteration in ethanol intake relative to nonlactating control females. However, because water intake was substantially elevated in the maternal rats, there was a net decrease in ethanol preference. The final experiment examined aggressiveness in chronically food-restricted male rats. In line with previous studies, this procedure increased ethanol drinking, but it did not enhance aggressive behaviour. It is concluded that, in our rats, there is no apparent association between the level of social aggression and the voluntary intake of ethanol in a two-bottle choice paradigm. The possibility remains, though, that alcohol drinking is better related to other forms of aggression, such as defensive or predatory aggression.

Nutritional ecology of dimorphic herbivores: digestion and passage rates in Nubian ibex.

We compared forage digestion and passage rates among three groups of Nubian ibex (Capra ibex nubiana) - mature males, non-lactating females, and lactating females - to test hypotheses relating intraspecific digestive ability to body mass and reproduction costs. We hypothesized that large males (60 kg) would exhibit longer forage retention times and more complete digestion of fermentable cell walls than adult females (23 kg). We tested these predictions by measuring digestion and retention of a grass hay and an alfalfa hay, forages that exhibited contrasting rates and extents of cell wall digestion. Consistent with predictions, males retained both forages longer than non-lactating females. However, by substantially increasing gut fill, lactating females increased both intake and retention time with respect to non-lactating females. Contrary to predictions, all three groups digested the grass (66% digestible) and alfalfa hay (63%) equally well. Alfalfa cell wall was less digestible than that of grass hay (60% vs 69% digestible), and retention time of alfalfa was consistently, but not statistically significantly, shorter. Fiber digestion was not correlated with retention time, emphasizing the ability of behavioral processes to modify digestion rate. We postulate that females achieved their greater digestion rate by masticating forages much more thoroughly than males.

Use of Bioelectrical Impedance Analysis (BIA) for Predicting Body Fat in Three Populations of Hibernating Black Bears

Bioelectrical impedance analysis (BIA) is a tool used to provide a measure of body water content and total body fat in an organism. Recently, researchers have validated BIA against tritiated water techniques in the laboratory and proposed it as a fast, non-invasive method for assessing body condition in free-ranging black bears. In the present study, we field tested BIA as a plausible tool for investigating body fat utilization during hibernation by three black bear populations in the Rocky Mountains. Body fat content in the fall ranged from a mean of about 39% for a group of large, lactating females down to about 29% by two groups of bears consisting of males and mostly non-lactating females. Daily rates of body fat use were greater for the larger, lactating female group than either of the other two groups. Although the fat data determined by BIA appear useful in terms of trends and relative changes, many of the absolute values are inconsistent and perhaps inaccurate. Because BIA is so sensitive to a variety of factors typical of field conditions, we recommend it not be used as the sole source for assessing body condition of large animals such as black bears.

Growth and Reproductive Patterns in the South American Fur Seal

We describe patterns of age-specific growth and reproductive rates for female South American fur seals, Arctocephalus australis , in Uruguay. Females achieve body weight of 41.7 kg at 10 years of age and adult length of 128.9 cm at 10 years of age. Pregnancy rates showed significant interannual differences, suggesting effects from environmental factors and demographic variability. Fetuses from lactating females were smaller than fetuses from nonlactating females. We suggest that simultaneous lactation and pregnancy affect the amount of energy devoted to embryonic growth.

Changes In Body Composition During The Postpartum Period

The common belief: that lactating women experience greater weight and fat loss than their non-lactating counterparts during the postpartum period has often been cited by pregnant women as an advantage of breastfeeding. We classified 28 women, aged 21 to 39. years, into 5 groups according to length of lactation. Group 1 consisted of 5 women non-lactating women. Group 2 breastfed solely 1–3 months and consisted of 5 women. Nine women were in group 3 whom breastfed solely 4–6 months. Group 4 consisted of 4 women who breastfed solely 7–9 months, and group 5 consisted of 5 women who: breastfed solely 10–12 months. Body composition measurements were taken at 1, 2, 3, 6, and 12 months postpartum and included body weight; percent body fat; bicep and tricep skinfold thickness; and maternal energy intake and expenditure. A steady but significant decline in mean maternal body weight occurred in all groups over the 12 month postpartum period (p=0.008); however, there were no significant differences between the 5 groups (p=0.703). Likewise, the percent body fat resulted in a significant decrease for all groups (p=0.005), while there was no significant difference between the groups (p=0.513). The bicep and tricep skinfold thickness did not change significantly between the groups during the 12 month postpartum period (p=0.688 and p=0.434 respectively). The calculated energy intake did not change significantly between groups during the 12 month postpartum period (p=0.139). In fact, the mean caloric level of all groups never actually reached the RDA level for non-pregnant, non-lactating females. Furthermore, the estimates of energy expenditure for maintenance and activity did not differ between the groups (p=0.564). These results do not support the cannon belief that breastfeeding facilitates greater weight loss in the postpartum period.

Reproductive Senescence in Female Japanese Monkeys (Macaca Fuscata): Age- and Season-Related Changes in Hypothalamic-Pituitary-Ovarian Functions And Fecundity Rates

Age- and season-related changes in gonadotropin-gonadal functions were studied in captive female Japanese monkeys (Macaca fuscata fuscata), with special reference to reproductive senescence. In experiment 1, a total of 57 nonlactating females at ages 3-32 yr were used. Blood samples were collected for at least one breeding season (September through March), and changes in plasma concentrations of LH, estradiol, and progesterone were examined. In experiment 2, two groups of females (older females, n = 5, over 21 yr old; mature females, n = 5, aged 8-12 yr) received s.c. injections of 50 micrograms/kg of estradiol benzoate during the mid-breeding season. In experiment 1, ovarian functions as well as fecundity rates were maintained in the animals aged 5-20 yr. A decline in ovarian activity became apparent at 21-25 yr of age, when animals exhibited a slight increase in plasma LH during the breeding season. Onset of menopause occurred at around 27 yr of age, near the end of the life span. Menopausal females exhibited a marked seasonal difference in plasma LH concentrations, with high levels during the breeding season. In experiment 2, estradiol treatment elicited an LH surge in both old and mature females. The marked seasonal difference in plasma LH, as well as the maintenance of LH response to estradiol in menopausal females, suggests a possibility that biannual changes in sensitivity of the hypothalamo-hypophysial axis to the negative feedback action of estradiol are maintained even after menopause.

Reproductive Behavior of Male Wood Bison in Relation to Progesterone Level in Females

In mammals, estrus commonly is identified by the behavior of males. However, the reliability of this indicator may vary with age or experience of males. We monitored fecal-progesterone levels in female wood bison ( Bison bison athabascae ) that were tended. Males tended females more often when females were close to estrus (fecal-progesterone levels 1 µg/g feces). In contrast, in an experimental population from which we removed mature males, subadults tended females in estrus longer than those not in estrus. Our results suggest that although tending behavior of males is a reliable indicator of the occurrence of an estrous cycle, the behavior of only dominant individuals is meaningful. Subadult males often tend anestrous females because young males are excluded from breeding by the more dominant, mature males, not because of a lack of experience. When investigating the relationship between male behavior and the female's ability to produce young, as determined by subsequent births, we found that lactating females were more likely to ovulate than nonlactating females; but, among ovulation females, lactating and nonlactating females did not differ in their probability of producing young. This finding suggests that reproductive status of a female affects mostly ovulation, not conception. Accordingly, males did not prefer to tend ovulating females of either reproductive status.

Effects of protein and energy intake, body condition, and season on nutrient partitioning and milk production in caribou and reindeer

We used captive caribou (Rangifer tarandus granti) and reindeer (Rangifer tarandus tarandus) to study the effects of energy intake, protein intake, dietary protein:energy ratio, date, and body condition on (i) body fat versus body protein deposition and (ii) maternal tissue deposition versus milk production. Energy intake was the only variable significantly affecting body mass (BM) changes in either breeding or nonbreeding adult females. Lactating and nonlactating females had comparable efficiency coefficients for net energy retention (60 and 65%, respectively), but the daily maintenance requirement for lactating females (457 kJ/BM0.75) was twice that for nonlactating individuals (232 kJ/BM0.75). In both lactating and nonlactating females, the proportion of tissue deposited as fat rather than protein increased between spring and fall but decreased with increasing fatness. Energy intake increased protein deposition in lactating females but increased fat deposition in nonlactating females. Milk water volume increased with maternal energy intake and decreased with calf age. However, production of milk dry matter, milk fat, and milk energy were not affected by maternal energy or protein intake, maternal body condition, or calf age. Production of milk lactose correlated with maternal energy intake, while production of milk protein correlated with the maternal dietary protein:energy ratio.

Steroid hormones and prolactin in the white whale (Delphinapterus leucas) of West Greenland

Testosterone, progesterone, oestrogen and prolactin concentrations were determined in serum and urine samples collected from white whales (Delphinapterus leucas) taken by Greenlanders in the autumn of 1989-1991 and during May 1992. Hormone levels following long vs short intervals between hunting and isolation of serum samples were compared, and a significant difference was seen in the oestrogen concentrations.&#x0D; In male white whales the testosterone levels were significantly higher in sexually mature animals as compared to immature animals, 4.14 vs 0.96 nmol/l in serum samples and 0.62 vs 0.11 creatinine index in urine samples, respectively.&#x0D; Hormone levels of immature, pregnant, lactating and resting female white whales were compared, and the pregnant animals had higher levels of progesterone than the nonpregnant animals, 29.1 vs 1.76 nmol/l in blood and 22.1 vs 0.54 creatinine index in urine, respectively. The oestrogen level was higher in urine from pregnant females, 2.43 vs 0.37 creatinine index, but concentrations in serum were not significantly elevated. Lactating females had higher serum prolactin concentrations than nonlactating females, 4.35 vs 1.97 μg/l, respectively.

Responses of maternal and non-maternal ewes to social and mother-young separation

The response to social deprivation in non-maternal non-pregnant ewes was compared with that in post-parturient ewes kept with their lamb. In addition, the response to separation from the lamb was investigated in lactating ewes at times ranging from 24 h to 2 months post partum. Ewes were observed for 5 min in a 2 × 4 m pen, either in the presence or in the absence of 4 adult conspecifics, after which lactating ewes were deprived of their lamb for a further 5 min. Results indicate that mothers of lambs did not react to isolation from adult conspecifics 24 h after parturition, in contrast to non-lactating females, which showed significant increases in high-pitch bleating, motor activity and eliminative behaviours ( p < 0.05 in all cases). On the other hand maternal females reacted very strongly to isolation from their lamb. For some behaviours (high-pitch bleats, nosings) response to separation remained quite high even in mothers of two-month-old lambs. However a clear decrease in responses was noted in most behaviours during the first month, and in some cases during the first week of lactation. Overall these results indicate that there is a dramatic decline in gregariousness during the peripartum period. The comparison of postpartum changes in maternal responses to lamb separation in isolated and grouped ewes suggests a combination of decreased maternal response to separation and recovery of usual social tendencies in the first weeks of lactation. Finally our results also indicate that the nosing of inanimate substrates such as ground and walls generally observed in open-field type tests may be related to social deprivation.

Suppressed copulatory behavior and ovarian function in lactating Japanese monkeys (Macaca fuscata fuscata) during the mating season

The influence of lactation on copulatory behaviors and ovarian functions was studied in Japanese monkeys (Macaca fuscata fuscata) during the mating season. Three lactating females were housed in an outdoor group cage with their infants, and three nonlactating females were housed in an adjacent outdoor cage. They were mated by introduction of one of four rotationally chosen males into the females' cage, for two hours three times a week; the occurrence of ejaculatory copulations was recorded. Blood samples were collected on each observation day, and plasma levels of estradiol, progesterone, and luteinizing hormone (LH) were measured by specific radioimmunoassays. In nonlactating females, plasma estradiol increased during the transition into the mating season, and rose to levels over 90 pg/ml for the first time on about 50 days before the first ovulation. Shortly after plasma estradiol exceeded 90 pg/ml in the nonlactating females, the onset of ejaculatory copulations occurred. They received ejaculations continuously up to the early ovarian luteal phase. On the other hand, in lactating females, there were lower levels of plasma estradiol (below 90 pg/ml) during the transition into the mating season, and they received no ejaculation during that period. Two of the three lactating females ovulated only once, and they received ejaculations only during the periovulatory period, coinciding with the rise of their plasma estradiol levels over 90 pg/ml. The remaining lactating female remained anovulatory and received no ejaculation throughout the entire mating season. These results have demonstrated that the low sexual activity of lactating females is clearly correlated with low levels of plasma estradiol due to suppressed ovarian function.

Ecological strategies of woolly monkeys (Lagothrix lagotricha) at Tinigua National Park, Colombia.

Information on the use of space, activity patterns, diet, and social interactions were recorded for a group of woolly monkeys (Lagothrix lagotricha) during 13 months at Tinigua National Park, Macarena, Colombia. In this region, fruit abundance changes throughout the year with a peak during March-April (beginning of the rainy season) and less fruit during September-November (end of rainy season). Woolly monkeys spent most of their time in mature forest where fruit abundance is higher than in opendegraded or flooded forests. Changes in habitat used by monkeys were coupled with changes in fruit supply across vegetation types. On an annual basis, woolly monkeys spent 24% of point samples locomoting, 36% resting, 36% feeding, and 4% on other activities. However, these proportions varied across the year depending on fruit availability. Based on instantaneous samples, the diet consisted mostly of fruits (60%), arthropods (23%), vegetative parts and flowers (17%), and other items (1%). Non-lactating females and juveniles spent more time eating insects than adult males and lactating females; however, significant differences between classes were detected only during the period of fruit scarcity. These differences are probably due to the high extent to which non-lactating females and juveniles were excluded from fruiting trees by males. The high proportion of arthropods in their diet is unusual for primates with large body size and is a possible factor influencing group cohesiveness in woolly monkeys. © 1994 Wiley-Liss, Inc.